Pen having an integrally injection-moulded coating sleeve

ABSTRACT

A pencil for applying a coloring and/or cosmetic substance, having a pigment core composed of the substance that is to be applied and a one-piece injection-molded casing encompassing the pigment core that is composed of a thermoplastic material that consists of a mix of a first plastic and a second plastic, wherein the casing, respectively viewed in the radial direction, has an outer enrichment zone with a higher concentration of the first plastic than in the middle region and the casing, respectively viewed in the radial direction, has an inner enrichment zone with a higher concentration of the first plastic than in the middle region.

BACKGROUND

The present disclosure relates to a sharpenable pencil, in particular acosmetic pencil, and a method for the production thereof.

Cosmetic pencils in which the pigment core is enclosed in a woodenpencil casing are widely used. The wooden pencil casings can be easilysharpened and resharpened by hand with the aid of a sharpener, whichfunctions according to the principle of a pencil sharpener.

The production of wooden pencil casings, however, is by nature quiteexpensive. It requires shaping wooden slats, gluing them, and thenseparating them by milling.

In situations in which pencils have to be produced not as graphitepencils or colored pencils, but rather as cosmetic pencils, otherspecific problems arise.

Cosmetic pencils usually require a higher quality of wood than coloredpencils. This is because as a rule, cosmetic pencils need to have asmoother tip. Cosmetic pencils also require a more or less costlysurface finish. The individual pencils are usually painted or coated oneor more times. This is because specifically as compared to an individualcolored pencil, high-priced cosmetic pencils must optically andhaptically give customers the impression of particularly high quality.

A typical method for producing such pencils, which is noncritical withregard to the pigment core compound as such, consists of extruding asuitable pigment core compound and gluing it into grooved slats orinserting it into plastic casings. This method corresponds to the methodthat has proven valuable in the production of colored pencils. In thisextrusion method, it is disadvantageous that as a rule, it is onlypossible to use pigment core compounds that yield relatively hardpigment cores. This is because the pigment cores must remain manageableduring the additional processing—pigment cores that are too soft run therisk of deforming when they are inserted into the slats that are to besubsequently glued together. Hard pigment cores, however, are oftenundesirable specifically in cosmetic pencils because they exhibit aso-called harder application in that a satisfactory quantity of cosmeticcan only be drawn from them by exerting a relatively high pressure.

Because of this, a different method for producing the pigment core isoften used in cosmetic pencil production. In this method, the cosmeticcompound is poured in a hot state into prefabricated shaft casings witha concentric hole in which the pigment core compound cools. But here,the problem arises that cosmetic compounds can contain a relatively highpercentage of components that are volatile (in the hot state). Even inthe cooled state, these volatile components tend to diffuse or migrate,at least over time.

In cosmetic pencils with soft pigment cores of this kind, it istherefore necessary to also perform a separate pretreatment of the innersurface of the wooden pencil casing that contains the pigment core—if awooden casing is even to be used in the first place. Special steps mustbe taken because it is necessary to prevent volatile components of thepigment core from diffusing into the wood or even from migrating withinthe wood and thus being drawn from the pigment core and possiblydamaging the paint on the outer surface. This problem can even alsooccur with plastics, particularly with foamed plastics. Volatilecomponents can even diffuse into plastics and, if they have penetratedthe plastic intensively enough after some time, may possibly damage theouter surface.

In order to remedy this problem, the German patent application DE 2 834479 proposes constructing a cosmetic pencil with a grease-based pigmentcore, which is provided with a metallic sheath before it is introducedinto the casing. A metallic sheath does produce a good barrier, butincurs unnecessary expense. It is also troublesome when sharpening thepencil. The metallic sheath can indeed be made very thin and provided inthe form of a foil, so to speak. But the long, narrow strips of foilthat are cut by the sharpener tend to become tangled because unliketrimmed-off wooden shavings, no breakage of the shavings occurs in thiscase.

The German patent application DE 31 37 4 86 A1 is devoted to the sameproblem. It proposes introducing the pigment core into a tube made of asharpenable plastic material; the tube is coated on the outside with alayer that is impermeable to solvents, for example in the form of aplastic film made of polyester. Such a design is not only expensive, butalso cannot meet the high optical and haptic requirements that areplaced on a cosmetic pencil. In addition, the film, if it is installedin the form of heat-shrink tubing, can wrinkle or produce generallyundesirable overlaps. The incorporation of a plastic film is alsoproblematic because the plastic film is cut into during sharpening andis not always cut off cleanly so that the sharpened end runs the risk ofquickly becoming unsightly. In addition, the problem of the lack ofshaving breakage arises, which has already been described above inrelation to the metal foil. These problems are known to the personskilled in the art, even if the patent application in question saysnothing about sharpenability.

European patent EP 0 613 634 B1 is also devoted to this problem. Itproposes producing a combined pencil casing, which consists of athin-walled plastic tube that is inserted into the receiving opening ofthe actual pencil casing. After the assembly of these two parts, thepigment core is then poured in. Obviously, the task of the insertedthin-walled plastic tube is to seal the pigment core and to remaindimensionally stable beyond the casting temperature of the pigment core.Because it is thin-walled, it does not stand in the way of thesharpening even if a comparatively hard plastic is used. On the otherhand, an easily sharpenable plastic can be used for the actual pencilcasing, which does not have to make allowances for the diffusionbehavior of the pigment core components.

In general, producing one-piece pencil casings out of plastic involvesconflicting objectives on a number of levels.

First of all, it is necessary to use a plastic that is soft enough topermit sharpening with a sharpener that functions according to theprinciple of a manual pencil sharpener. Then, the plastic must at thesame time be dimensionally stable beyond the casting temperature of thepigment core. Finally, the plastic must produce the most attractivepossible surface, in order to provide the desired optical, haptic, andhigh-quality appearance with the least possible amount of finishingwork.

In this respect, in order to find a workable compromise, often plasticsthat are inherently relatively hard are used for producing the pencilcasing. These have the necessary durability. The sharpenability in thiscase is usually insured by the fact that the plastics are foamed. Foamedplastics, however, cannot be processed by injection molding, insteadmaking it necessary to produce the pencil casing by means of extrusion.The foaming and the extrusion, however, cause the surface quality tosuffer so that pencil casings of this kind are not easy to sell withoutfinishing treatment.

One example of this is U.S. Pat. No. 5,360,281, which claims protectionfor pencil casings made of foamed plastic. This patent does indeed alsomention the concept of producing pencil casings by means of injectionmolding, but the concept was not incorporated into the claims—clearlybecause the proposed plastics exhibit an excessively poor sharpenabilitywhen not foamed.

Finally, US patent application 2013/0121747 A1 should also be mentioned,whose stated object is to produce pencils with a pencil casing that isparticularly reliable from a chemical and mechanical standpoint. Theintent is to achieve this by choosing a plastic mix that does notrelease any VOC during production and use and which breaks in asplinter-free way so that the corresponding pencils are also suitablefor small children. In addition, the pencils should also be easy tosharpen.

In order to solve this problem, this US patent proposes producing thepencil casings from a plastic mix that consists of

-   -   at least one styrene-butadiene copolymer,    -   at least one styrene-butadiene-styrene block copolymer,    -   and at least one other plastic from the group of styrene        polymers, styrene-acrylonitrile polymers,        acrylonitrile-butadiene-styrene polymers, acrylic styrene methyl        methacrylates, or a combination of the above-mentioned plastics,    -   as well as at least one auxiliary material.

This US patent application does not address the above problems in theproduction of cosmetic pencils. In particular, the application does notaddress either the problems that arise during pigment core casting orthe problem of how a high-quality outer surface can be achieved. This USpatent also does not provide any satisfactory solution to the problemrecognized therein of the migration of pigment core components. The USpatent proposes counteracting the drying-out of pigment cores withvolatile components by adding waxes to the plastic mix from which thecasing is produced. This solution, however, is insufficient particularlyin the cosmetic sector since it is not possible to guarantee that thetechnical waxes that are added to the plastic will not themselvesmigrate into the pigment core, which is undesirable because onlycosmetically approved, harmless substances can be added to the pigmentcore.

SUMMARY

By contrast, in a first step, an aspect of the present disclosure is todisclose a pencil that is for applying a coloring and/or cosmeticsubstance, that has a one-piece casing consisting entirely of plastic,that can be sharpened preferably using a pencil sharpener, and has apreferably glossy high-quality outer surface, which requires no furtherfinishing after the injection molding except for the attachment of apossible label or other mostly localized decorations.

The pencil according to the present disclosure has a pigment corecomposed of the substance that is to be applied, with or withoutvolatile components, and encompassing the pigment core, a one-piece,single-substance injection-molded casing that is composed of athermoplastic material that consists of a mix of a first plastic and asecond plastic, each of which, in pure form, has different properties.

In the context of the present disclosure, injection molded “of a singlesubstance” means that only a single material (even if it is composed ofa mix) has been injected into the mold cavity, usually in a single shotor in exceptional cases, in several successive shots. This contrastswith “overmolding” in which a first material is first injected into themold cavity and then—from a different material supply—a second materialthat has other properties is injected onto it.

The pencil according to the present disclosure features the fact thatthe first and second plastics are chosen so that they partially separateas a result of the injection molding and thus form a casing, which,viewed in the radial direction, has a higher concentration of the firstplastic in the region of its surface of the outer circumference (outerenrichment zone) than in the middle (central depletion zone). At thesame time, the first and second plastics are chosen so that the casingalso has a higher concentration of the first plastic.

The pencil according to the present disclosure also features the factthat it can be sharpened using a sharpener that functions according tothe principle of a pencil sharpener, i.e. by rotating the pencil byhand.

To make the determination according to the present disclosure as towhether a pencil is sharpenable, there are various alternative criteriathat in the ideal case, are cumulatively fulfilled:

-   -   With the manual sharpener at the end of the pencil, whose        continuous cone corresponds to the angle at which the sharpener        blade is positioned, it is possible three times in immediate        succession to remove a continuous shaving over at least five or        better still at least eight full pencil rotations. In other        words, the shaving forms a continuous curl, preferably with a        thickness that remains constant over the entire length        (fluctuating by +/−10%) and ideally without a thickness increase        of more than 15%, or better still only 10%, being observed        toward the end of the shaving.    -   The generally conical cut surface that such a sharpener leaves        behind is preferably uniformly smooth in this case. Apart from        local step edges that can mark the position reached by the        sharpener blade when the sharpening procedure is terminated, it        preferably has no local break-outs, chipping, or steps, for        example in the form of chatter marks or in any case does not        exhibit any local break-outs, chipping, or steps with a depth of        more than 0.3 mm.

It is generally the second plastic, which is chosen so that it ensuresthat the casing can be sharpened by means of a sharpener like a pencilsharpener. The measure for this is a comparison to a pencil that has anidentically dimensioned casing, which is entirely composed of the firstplastic and cannot be sharpened in the above-described way.

Thus in one go, so to speak, a multi-layer casing is obtained, which upto this point, could only be produced with a significantly more complexovermolding method in which first, the one casing part is injectionmolded out of the first material and then, after the removal of movablesliders, the second casing part is injection molded onto it out of thesecond material.

The pencil according to the present disclosure features the fact thatthe properties that are inherent to the first plastic in its pure formare distinctly accentuated due to the enrichment of this first phase atthe surface of the outer circumference and inner circumference, whichenrichment is forced into existence with the aid of the injectionmolding process, even if a certain percentage of the second plastic isstill present right at the respective surface. In this way, the firstplastic, in one and the same original forming process, produces a layerwith a high surface quality on the surface of the outer circumference ofthe pencil casing. With a correct choice of the first plastic, thesurface—viewed with the naked eye—can be absolutely flat and as smoothas glass. In addition, on the surface of the inner circumference of thepencil casing, a layer is formed that performs a barrier function. Thisbarrier function will be explained in greater detail later. It has apositive influence on the casting of the pigment core and/or on theshelf life of the pigment core.

According to the present disclosure, a sharing of tasks is providedhere. The first plastic is chosen so that an outstanding surface qualitycan be achieved. If the first and second plastics are correctly matchedto each other so that the necessary mix is produced, then it is thuspossible to achieve a surface that exhibits a mirror-like shinecomparable to the shine of the finish on a piano.

It is not necessary to take into account sharpenability when choosingthe first plastic. This is because the outer enrichment zone—in whichthe first plastic is preferably enriched to more than 80% by weight orbetter still enriched to more than 90% by weight on the outside—can bekept thin in the radial direction, if need be much thinner than inovermolding.

The same is mostly true for the inner enrichment zone in which the firstplastic is enriched to at least ≥70% by weight on the inside.

Ideally, the dimension RAA and/or RIA of the outer and/or innerenrichment zone is 0.075 to 0.5 mm or better still only up to 0.35 mm,measured from the surface of the outer circumference and/or innercircumference toward the inside in the radial direction. As a result,the first plastic does not hinder the sharpenability, even though ittends to have a rather poor machinability.

For the achievement of the respective function, it has turned out to beadvantageous if the inner enrichment zone has a slightly smaller radialdimension RIA than the outer enrichment zone, whose radial dimension isRAA. In other words, preferably the following applies: RAA>RIA andideally even RAA>RIA*12/10.

With a correspondingly intensive cooling of the injection mold at theplace in which it forms the outer enrichment zone, it is possible toachieve the fact that the exposed surface of the outer enrichment zoneconsists, at least up to 95% by weight, in some cases even up to 97% byweight and more, of the first plastic (and the pigments possiblyincorporated into it).

Within the entire outer enrichment zone, the percentage of the firstplastic is ≥80% by weight or significantly better still, ≥90% by weight.

With a correspondingly intensive cooling of the injection mold at theplace in which it forms the inner enrichment zone, it is possible toachieve the fact that the percentage of the first plastic within theentire inner enrichment zone is at least ≥67% by weight or better still,≥70% by weight.

Correspondingly, this is generally accompanied by a central depletionzone. Within this central depletion zone, which is in the middle of thecasing, the local percentage by weight of the first plastic is reducedrelative to the percentage by weight that the first plastic had in theinjection molding mix that was prepared for the injection molding. Inany case, the expression “the middle of the casing” means a region of+/−0.75 mm or at least +/−0.5 mm around the region of the radius that iscalculated as the average of the radius at the surface of the outercircumference and the radius at the surface of the inner circumference;the average radius is used in the event of non-round contours.

Depending on the percentage of the first plastic in the plastic compoundthat is injection molded into the mold cavity, the percentage of thefirst plastic within the entire central depletion zone is preferably atleast ≤60% by weight or better still, ≤55% by weight.

By contrast, for the second plastic, a plastic can be chosen that, inthe places in which it is definitively involved in the formation of theplastic structure, it reduces the strength of the first plastic even ifthe first plastic possibly makes up the larger percentage by weight ofthe overall mix. Thus when choosing the second plastic, it is notnecessary to take into account its surface quality and/or thebarrier-forming capacity relative to pigment core components since thesecond plastic is not definitively involved in the formation of thesurfaces.

The production of the casing of the pencil by means of injection moldinglends the pencil a particular physical property in the present case.This is because in this instance, the injection molding itself causesthe first plastic to be enriched at the surface of the outercircumference, thus forming the surface that possibly has a finish likea piano—even though the first and second plastics were uniformly mixedbefore being injected into the injection mold.

It is true that the reasons why such a segregation occurs have not yetbeen completely explained. It is nevertheless clear that when the mix ofthe first and second plastics, which is injected into the mold, comesinto contact with the well-cooled surface of the mold cavity, thisinitially results in an abrupt cooling. This cooling causes asegregation to occur because the one plastic solidifies more quicklythan the other plastic.

In this way, the well-cooled surface of the mold cavity is coated with alayer that entirely or predominantly consists of the first plastic. Theresulting layer is usually very hard or harder than the underlying coresince the percentage of the second plastic contained therein cannotproduce a definitive disrupting effect.

Since the above-mentioned layer, because of its poor thermalconductivity, constitutes an insulation, a further abrupt cooling isprevented. This results in the fact that below the above-mentionedlayer, the separation decreases, usually in rapid fashion. In themiddle, therefore, the mix of the first and second plastics as such isalso retained in the course of the solidification, even if as a rule, achange in the percentages by weight is observed. Since the secondplastic disrupts the structure, the solidified layer is less strong inthis region than the above-mentioned layer, which has formed against thecooled surface of the mold cavity.

The term sharpener or pencil sharpener in this case refers to theclassic pencil sharpener of the kind that is used for graphite pencils,colored pencils, and cosmetic pencils. Such a pencil sharpener has abody made of metal, wood, or plastic, which has a conical opening forthe tip of the pencil that is to be sharpened and at least one blade,which removes a shaving from the tip when the pencil is rotated by hand.

The term thermoplastic material in this case refers to a material,which, by heating, can be brought into a viscous state in which it canbe injection molded. The term covers classic thermoplastics and TPEs.

The first and second plastics are chemically different, i.e. generallybelong to different material classes or plastic types.

The above definition of the different terms also applies to that whichis stated below unless otherwise clearly indicated by the context.

Additional Modifications

The concentration of the first plastic preferably decreases continuouslyfrom the outer enrichment zone and from the inner enrichment zone towardthe middle.

This distinguishes the pencil according to the present disclosure ormore specifically its multi-layer casing, from known casings, which onlyobtain their two-layer or multi-layer nature because a continuousadditional plastic layer, a continuous film, a continuous paint layer(“piano finish”), or the like has been applied.

Naturally, at the end, the casings according to the present disclosurecan also be provided with additional layers of plastic or paint, inparticular for partial additional decoration, and with foils, e.g. forlabeling purposes.

Preferably, the casing is composed of both the first and second plasticsacross its entire cross-section, but with the two plastics being foundin percentages by weight that differ from one location to another,generally in such a way that the percentages by weight changecontinuously along the cross-section (viewed in the radial direction).In some cases, the term “overall cross-section” does not include theboundary layer in the region up to 0.2 mm below the surface of the outercircumference. The same is true for the boundary layer in the region upto 0.2 mm below the surface of the inner circumference.

Ideally, the casing has a separate layer only in the vicinity of thesurface, e.g. in the form of the removable skin explained below, anddoes not have a slate-like structure over the entire cross-section. Thisis because this would undesirably increase the tendency for the shavingthat is peeled off during sharpening to spontaneously disintegrate intoextremely fine crumbs and thus cause soiling even of the cosmeticpigment core.

The barrier layer can be a mechanical barrier layer that is very smoothand thus prevents air inclusions from occurring during the pouring ofthe pigment core—of the kind that are frequently observed when pigmentcores are poured into wooden casings whose inner surface is relativelyrough.

Instead of this or at the same time, the barrier layer can be a chemicalbarrier layer, which is clearly preferable. Such a barrier layerfeatures the fact that it restricts migration of pigment corecomponents. Depending on the choice of the first plastic, thisparticularly limits the migration of isoparaffins and silicones and/orthe migration of water and polar volatile substances such as alcohols.It achieves this if it reduces the migration to such an extent that noperceptible harm (hardening/drying) to the pigment core is observed evenafter storage for 12 months at a constant temperature of 23° C. In anycase, one speaks of a barrier layer in the narrower sense when inrelation to isoparaffins and silicones and/or in relation to water andpolar volatile substances such as alcohols, the first plastic (in pureform) has a lower diffusion coefficient than the second plastic phase inpure form.

It has turned out to be particularly advantageous to use as the firstplastic a weakly polar plastic with an electronegativity difference ΔENin the range between 0.3 and 0.5 inclusive, but which contains a monomercomponent or a block that enables weak interactions with anotherstrongly polar plastic so that an immediate, spontaneous separation isprevented. The term electronegativity difference ΔEN is understood hereand below to mean the maximum electronegativity difference betweenadjacent atoms in the polymer structure.

In this case, it is particularly advantageous to use a plastic from theclass of styrene acrylonitriles or acrylonitrile-styrene copolymers(abbreviation: SAN, nomenclature here and throughout in accordance withDIN EN IDSO 18064), preferably in pure form. SAN is weakly polar, but bymeans of the acrylonitrile component within it, can also haveinteractions with other strongly polar plastics.

A preferable composition consists of 65% by weight to 80% by weightstyrene and of 20% by weight to 35% by weight of acrylonitrilecomponents as well as respectively different molar masses. Aparticularly advantageous composition consists of 70% by weight styreneand 30% by weight acrylonitrile components (each with a tolerance of+/−1.5%). Ideally, the styrene acrylonitrile sold under the brand name“LURAN 378P™” by the company BASF SE, Ludwigshafen, Germany, is used.

Styrene acrylonitriles and to a particular degree, LURAN 378P™, in theform in which they are (not at all or essentially not) mixed with otherplastics, are characterized by their chemical resistance, particularlyeven relative to amines, which are frequently used as neutralizingagents in cosmetic compounds. Styrene acrylonitriles and to a particulardegree, LURAN 378P™, are also characterized by their dimensionalstability in the presence of heat. These properties are used here inconnection with the separation according to the present disclosure inthe course of the injection molding in order to lend the surface on theinner circumference of the casing its superior properties.

At the same time, styrene acrylonitriles and to a particular degree,LURAN 378P™, are characterized by their exquisite appearance on thesurface, which is used here in connection with the separation accordingto the present disclosure in the course of the injection molding inorder to lend the surface on the outer circumference of the casing thenecessary surface quality.

In a known way, styrene acrylonitriles and to a particular degree, LURAN378P™ inherently exhibit a high strength, in particular a high scratchresistance, and are brittle. Sleeves made of pure styrene acrylonitrilestherefore cannot easily be sharpened using a pencil sharpener and thenormal exertion of force.

According to the present disclosure, the second plastic is chosen sothat it weakens the strength of the first plastic in the places wherethe casing does not need to be characterized by the special propertiesof the first plastic.

In general, it can be said that the second plastic should preferably bea plastic, which, in the course of the injection molding, separates outfrom the SAN by means of separation phenomena and is inherently wettedphysically by means of microphase separation, by forming partiallycrystalline regions.

Preferably, the second plastic is a polar plastic with anelectronegativity difference ΔEN in the range between >0.5 and 1.7.

It has turned out to be particularly advantageous to use a plastic fromthe class of polar thermoplastic elastomers (abbreviation TPE-ET),preferably in pure form, as the second plastic.

In particular, the TPE-ETs that are used are those that employ apolyether group as a soft segment. It has turned out to be particularlyadvantageous to use the members of this class belonging to the sub-classof polar thermoplastic polyester elastomers or polar thermoplasticcopolyesters (abbreviation TPC-ET). Typically, this plastic consists ofa block copolymer with alternating hard and soft sections and thechemical interactions are essentially ester-based and/or ether-baseddipolar interactions. Ideally, what is used is the polar thermoplasticcopolyester produced under the brand name “Arnitel EM400™” by thecompany DSM Engineering Plastics BV, Urmonderbaan 22, 6167 RD Geleen,The Netherlands.

The astonishing thing is that the mix of the above-described first andsecond plastics, in the place where it has not extensively separated (inthe sense that the SAN concentration does not fall below 90% by weight),has a lower strength than would be expected of the individualcomponents. This results in a good sharpenability. In this case, theonly limited resistance of the second plastic here to the volatilecomponents of soft pigment core compounds does not matter since thefirst plastic on the surface, which comes into direct contact with thepigment core compound, constitutes a barrier layer, as explained above.Furthermore, it also does not matter that a mirror-like surface cannotbe achieved with a TPE or TPC-ET.

Alternatively a plastic from the class of acrylonitrile ethylenepropylene styrenes (AES) can be used as the first plastic.

Ideally, the acrylonitrile ethylene propylene styrene sold under thebrand name “ROTEC A702™” by the company ROMIRA Gesellschaft für Vertrieb& Verarbeitung von Chemieprodukten mbH, Pinneberg, Germany is used.

In principle, it also seems to be conceivable to use a system in whichthe first plastic has a weight proportion of 20% by weight to 80% byweight, the second plastic has a weight proportion of 80% by weight to20% by weight, and the fillers or auxiliary materials have a weightproportion of 0% by weight to 30% by weight or better still, only up to15% by weight. Impurities of any kind are undesirable and are preferablyavoided above the per mil range, in particular above 15 per mil byweight. To the extent that this is not possible in the individual case,impurities of up to 5% by weight or better still, up to 2.5% by weight,can be tolerable.

In order to achieve the effect according to the present disclosure,however, it has turned out to be particularly advantageous to set up thesystem such that the first plastic has a weight proportion of at least45% by weight or better still, at least 55%. Usually, the recommendedupper limit for the first plastic is then 75% by weight or better still,65% by weight auxiliary materials and pigments with a weight proportionof up to 15% or better still, only up to 5%.

Astonishingly, it has turned out that adding other plastics to thebinary system (composed of SAN or AES and TPE-ET or TPC-ET) can have anegative impact on whether it has the simplest possible adjustability.For this reason, the first and second plastics constitute at least thepredominant part of the plastics used for the casing. This means thatthe casing according to the present disclosure consists of the first andsecond plastics in that these phases constitute the overwhelming part ofthe plastic compound or in some cases, at least 90% by weight of theplastic compound used. The best case is the one in which the first andsecond plastics and the pigments and auxiliary materials—or just the twoplastics together with the pigments that are added to them—constitutethe entire plastic compound used for the casing, apart from impurities.

Otherwise, as stated above, fillers that influence the plastic matrixbut are not involved in its structure and auxiliary materials such aspigments can be added. Gas-forming agents or foaming agents inquantities that negatively affect the injection molding are to beavoided, preferably completely avoided.

The auxiliary materials also include plastic constituents, which,depending on the type of auxiliary materials, are merely poured into thematrix of the first and second plastics and are not melted in the courseof the injection molding, for example a cross-linked elastomer orthermosetting polymer that is added in a ground form as a filler.Preferably, though, such fillers, which are themselves composed ofplastic, are avoided since they can increase the viscosity and canhinder the separation.

Preferably, the first plastic is chosen so that at the outercircumference surface, the casing has a mathematically determined glosslevel GU of more than 30 GU or better still, more than 40 GU. Themeasurement is performed in accordance with ISO 2813 along a span of 10mm at 10 evenly spaced measurement points in the direction along thelongitudinal axis L at a measurement angle of 60°.

Other effects, advantages, and embodiment possibilities of the presentdisclosure can be inferred from the embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the casing of a pencil according to the present disclosurein a longitudinal section through the center.

FIG. 2 shows the entire pencil according to the present disclosure in alongitudinal section through the center.

FIG. 3 is an enlarged detail and shows a part of the fracture plane of acasing that has been torn apart along its longitudinal axis.

FIG. 4 shows a section perpendicular to the central longitudinal axisthrough the casing of a pencil according to the present disclosure.

FIG. 5a shows an overview of the skin detachment test at the beginning,after the incision.

FIG. 5b shows a detailed view of the skin detachment test as itprogresses further.

FIG. 6 shows the respective RAMAN spectra for SAN and TPC-ET.

FIG. 7 shows the RAMAN spectra for SAN and TPC-ET for the puresubstances and at 2 different measurement points 100 and 200 on thesectional plane of the casing.

FIG. 8 shows the RAMAN intensity of the spectra recorded for samplesthat contained 0% by weight SAN, 30% by weight SAN, 50% by weight SAN,70% by weight SAN, and 100% by weight SAN and the complementarypercentages of TPE-ET.

FIG. 9 shows the steps in which the sectional plane of the casing, whichwas produced according to the 1^(st) embodiment, was measured usingRAMAN spectroscopy.

FIG. 10 shows how the concentration of SAN and TPC-ET changes in theradial direction over the cross-section of the casing.

DETAILED DESCRIPTION First Embodiment

For the first embodiment, 60% by weight SAN (LURAN 378P™) and 40% byweight TPC-ET (Arnitel EM400™) with the addition of 3% pigments(preferably black pigments of the usual type carbon black CI 77266,which is available from various companies) are brought into theinjection molding-ready, viscous state at a temperature of preferably250° C.+/−10° C. and are uniformly mixed in the process. No otherfillers or auxiliary materials are added. An extruder from the companyLeistritz, 90459 Nuremberg, Germany, can be used for this.

The actual injection molding procedure can be carried out with aninjection molding machine of the E-motion 940/160T type made by thecompany Engel, 90451 Nuremberg, Germany. The prepared compound is shotinto the molding cavity of the injection mold at an injection pressureof approx. 1400 bar. The injection mold in this case is cooled by meansof a liquid medium, which flows through the injection mold—sealed offfrom the mold cavity. In particular, the core pin of the injection mold,which forms the cavity that is provided to subsequently accommodate thepigment core in the casing, is itself directly cooled by the liquidmedium. In other words, the cooling medium flows through the core pinitself.

Then the demolding is carried out, preferably by removing the core pinand the casing together from the mold cavity and then sliding the casingoff of the core pin.

The casing 2 produced in this way particularly preferably looks like theone shown in FIG. 1; the structural details of the casing 2 will bediscussed in greater detail below.

The casing produced in this way exhibits an extremely scratch-resistantouter circumference surface with a finish like a piano. It is veryresistant to the migration of pigment core components and is easy todecorate.

In order to obtain a cross-section that permits visual inspection, thecasing 2 according to FIG. 1 was clamped into a tensile testing machineand torn into two halves by means of correspondingly high tensile forcesin the direction along its longitudinal axis L. FIG. 3 shows an enlargeddetail of the resulting fracture plane of the cross-section 3, in aninitial visual assessment by microscope.

It is already clear from FIG. 3 that a different layer has formed on anddirectly under the surface of the inner circumference 5 and the outercircumference 4. This finding was verified with measurements using RAMANspectroscopy, as explained in detail below. The results of this areshown in FIG. 4.

As is apparent, the one outer enrichment zone 6 and an inner enrichmentzone 7 are discernible. The characteristics of the outer enrichment zone6 and inner enrichment zone 7 can be influenced by means of thetemperature of the surface that is produced inside the mold cavity. Thecolder the corresponding surface of the mold cavity is at the beginningof the injection, the more pronounced the separation is. This alsoapplies to the inner enrichment zone 7. As already mentioned above, thetemperature of the core pin that produces the inner enrichment zone canbe controlled by providing a more or less intensive flow of the coolingmedium through the core pin itself.

In the present instance, within the limits of measurement accuracy usingRAMAN spectroscopy, no amount of the second plastic can be found on theexposed surface of the outer enrichment zone. This is not only desirablein the context of this embodiment, but is also generally preferred. Thisis because such a formation is advantageous for achieving the glossysurface desired here, which resembles the finish of a piano. In theradially inward direction below the exposed surface, the percentage ofthe first plastic begins to decrease. Down to a depth of approximately0.2 mm, however, a percentage of the first plastic of more than 90% byweight is present.

It is interesting that in any case in the region of the outer enrichmentzone, there appears to be a definite boundary layer starting at whichthe strength of the plastic that forms the wall of the casing decreasessignificantly. If a casing that has been produced according to thisfirst embodiment is cut diagonally with a blade so that a diagonallyprotruding shaving is produced, as shown in FIGS. 5a and 5b , it is thenpossible to peel a skin off the surface of the casing by pulling on theshaving with the unaided hand, regardless of the depth of the cut. Theskin is relatively strong and in most cases, only tears after adetachment length of 4 cm or more has been pulled off.

In general, in a way that is applicable beyond this embodiment, it canbe said that skin detachment tests of this kind have shown that aparticularly good sharpenability is achieved whenever such skins can bepulled off with a thickness of 0.08 mm to 0.25 mm.

To the extent that it has been possible to explain up to this point, itappears to be the case that the sharpener blade is then not reliant onhaving to completely cut the relatively strong skin and instead, itappears that a mix of cutting and tearing occurs, which has afacilitating effect.

Second Embodiment

To produce the second embodiment, 60% by weight AES (ROTEC A702™) and40% by weight TPC-ET (Amitel EM400™) with the addition of 3% pigments(preferably black pigments of the above-mentioned type) are brought intothe injection molding-ready, viscous state at a temperature ofpreferably 250° C.+/−10° C. and are uniformly mixed in the process. Noother fillers or auxiliary materials are added.

This compound, as described above for the first embodiment, is processedwith the aid of the machines described therein, which is also true forthe injection molding.

The casing 2 produced in this way particularly preferably looks like theone shown in FIG. 1.

The casing produced in this way exhibits an extremely scratch-resistantouter circumference surface with a silk-matt gloss. It is resistant tothe migration of pigment core components and is easy to decorate.

The tests using RAMAN spectroscopy, as will be explained in greaterdetail below, demonstrate that when this plastic mix is injectionmolded, a readily apparent outer enrichment zone and an inner enrichmentzone that is just as readily apparent are formed, whose magnitude varieswithin the above-described ranges depending on the intensity of thecooling of the injection mold.

Comparison Example

For the comparison example, 60% by weight SAN (LURAN 378P™) and 40% byweight of a usually non-polar SBS block copolymer (ALLRUNA W55™) withthe addition of 3% pigments (preferably black pigments of theabove-mentioned type) are brought into the injection molding-ready,viscous state at a temperature of preferably 250° C.+/−10° C. and areuniformly mixed in the process. No other fillers or auxiliary materialsare added. ALLRUNA W55™ is a brand name of the company ALLOD WerkstoffGmbH & Co. KG, 91593 Burgbernheim, Germany.

This compound, as described above for the first embodiment, is processedwith the aid of the machines described therein, which is also true forthe injection molding.

The casing 2 produced in this way particularly preferably looks like theone shown in FIG. 1.

The casing produced in this way exhibits a matte outer surface andneither a significant outer enrichment zone nor an inner enrichmentzone. Instead, the materials remain homogeneously mixed untilsolidification. The skin detachment test also cannot be performedbecause the casing clearly has a homogeneous strength.

RAMAN Spectroscopy for Determining Concentration

For ascertaining the concentrations that are particularly found in theouter and inner enrichment zones according to the present disclosure,RAMAN spectroscopy is the method of choice.

The above-described fracture plane turned out to be poorly suited to theperformance of a RAMAN spectroscopy. Instead of this, the tests wereperformed on a cross-section that was produced by first cutting orsawing through the casing transversely to its longitudinal axis and thecross-section that had thus been exposed was then ground.

To clarify the local proportions of SAN and TPC-ET, the RAMAN spectrawere measured across the cross-section of the casing that had beenproduced according to the first embodiment. The measurement wasperformed with a RAMAN spectrometer from the Almega series produced bythe company Thermo Fisher Scientific, 168 Third Avenue, Waltham, Mass.USA 02451.

In order to calibrate the device and be able to assign the individualparts of each respective spectrum, first the raw materials weremeasured. In other words, plates were produced that consisted of up to100% by weight SAN and up to 100% by weight TPC-ET. If a measuring pointcomes to rest fully on the respective plate and the thickness of theplate exceeds 2/10 mm, then the dimensions of the test pieces do notmatter. Individual measurements were performed on the two plates bythemselves.

The spectra obtained in this way were plotted in the graph according toFIG. 6. The dot-and-dash line shows the spectrum recorded for SAN andthe solid continuous line shows spectrum recorded for TPE-ET.

The area of the peak that reaches its maximum at 3050 cm−1 was used forthe SAN ascertainment; the area of the peak whose maximum is at 2250cm−1, which is also characteristic for the SAN, could likewise be used;it yields comparable values and therefore does not have to be separatelyconsidered below and can instead be disregarded.

Then the points 100 and 200 identified in FIG. 4 were measured one afterthe other. The two spectra recorded in this case were superposed asshown in FIG. 7. It is already clear from these figures that differentconcentrations of SAN and TPC-ET are found at the points 100 and 200.

Then in addition to the above-mentioned samples containing 0% by weightand 100% by weight SAN, different mixes of SAN and TPC-ET aresystematically produced and, through suitable temperature control,processed to produce the above-mentioned boundary layer-free plates,namely mixes that contained 30% by weight, 50% by weight, and 70% byweight SAN and the complementary percentages of TPC-ET. The RAMANintensity of the spectra that were recorded for the individualrepresentatives of this sample series were plotted in the graph that isshown in FIG. 8. In FIG. 8, it is clear that each mixing ratio can beassigned to a characteristic RAMAN intensity and there is a linearrelationship between the percentage by weight of the SAN, the TPC-ET,and the respective RAMAN intensities that are to be measured for them.

Then—as has been described above—the ground cross-section of the casing2, which was produced in accordance with the first embodiment, wasmeasured in a way that matches the sequence shown in FIG. 9 step forstep. Measurements were carried out point by point starting from theoutside and continuing in the radial direction to the middle of thecasing cross-section and carried out point by point starting from theinside and continuing in the radial direction to the middle of thecasing cross-section.

These measurements yield the graph that is shown in FIG. 10. The plasticcompound used for the injection molding had a mixing ratio of ⅔ SAN to ⅓TPC-ET. Starting from this and taking into consideration the spread ofmeasurement results, it is evident that a partial separation hasoccurred during the injection molding process in the injection moldingtool.

In this case, the concentration of SAN at the surface of the outercircumference surface of the casing is approx. 100% by weight.

At the surface of the inner circumference surface, the concentration ofSAN is only approx. 70% by weight.

The Structural Embodiment of the Pencil

The pencil 1 according to the present disclosure is embodied as shown inFIGS. 2, 3, and 4. As a rule, it has an outer diameter of approx. 6 to16 mm.

At its center, it has a receptacle for the pigment core 8 thatadvantageously constitutes a form-fitting rotation prevention means. Itscross-section can be circular, but is preferably oval, polygonal, oroctagonal in order to insure a better hold between the pigment core 8and the casing 2. The distance between opposing flat sides of theoctagon is preferably between 3 and 5 mm. The wall thickness of thecasing 2 is preferably in the range from 1.5 to 3 mm. The length of thepencil 1, i.e. its length in the direction of its longitudinal axis L,is generally greater than 85 mm, usually greater than 100 mm, and up to180 mm.

The receptacle for the pigment core 8 preferably extends through theentire casing 2 in the direction of its longitudinal axis L, i.e. as asemifinished product, the casing 2 forms a tube. This facilitates thepigment core casting. This is because at the end at which it forms thecone that is to be described in greater detail below, the casing, forpurposes of the pigment core casting, can be inserted into a mold thatseals it shut and then in the same way, gives the end of the pigmentcore in the region of the cone a corresponding, as a rule likewiseconically tapering, shape. The pigment core compound is then poured infrom the other end of the casing at which the seat is located and fillsthe pigment core receptacle in the casing 2 and the mold cavity thatmodels the tip of the pigment core 8. A casing consisting of plasticlike the one according to the present disclosure can be insertedparticularly well into a mold that closes it in a sealed fashion forpurposes of the pigment core casting since the plastic of the casing,compared to a wooden casing, is reversibly elastic, i.e. can be insertedor clamped into a corresponding mold in a sealed fashion. The verysmooth outer surface of the casing helps to achieve a reliable seal.

The one end of the pencil 1 tapers to form a cone 12, preferably with acone angle Pi of between 20° and 60°. In this way, this end contributesto producing the sharpened end that is known from a normal wooden penciland thus to form a starting surface, which in the first sharpening iscorrectly positioned relative to the sharpener blade and enables thesharpener blade to remove a shaving over its entire length.

The other end of the pencil 1 preferably has a seat 9 in the form of arecessed region on its outer diameter. A closing cap 10 can be placedonto this seat and preferably, a detent engagement is produced betweenthe seat 9 and the closing cap 10. In order to preserve the pigment coreas much as possible and to prevent migrations, an additional seal isusually provided under the cap, often in the form of a stopper orsilicone stopper 11. At the end where the pigment core 8 protrudes outfrom the casing 2, the finished pencil 1 is generally kept fresh bymeans of a cap 12 that is placed onto it. The very smooth andscratch-resistant outer surface that is achieved according to thepresent disclosure fosters the ability of the cap 10 to be slid on in agood and reliable way. The surface achieved according to the presentdisclosure is so scratch resistant that even after removing andreplacing the cap 10 thirty times, no dulling of the surface over whichthe cap 10 travels occurs that is visible to the naked eye due tomicro-scratches and the like extending in the direction of thelongitudinal axis of the pencil. The cap 10 is embodied so that it isslightly undersized, i.e. with a slightly smaller inner diametercompared to the outer diameter of the casing 2. The cap 10 that isproduced in this way can be slid onto the surface of the casing 2, whichis achieved according to the present disclosure, in a suction-inducingfashion and because of its smooth property, can also be pulled off fromit again (no stick/slip).

CONCLUDING GENERAL REMARKS

Independent protection, possibly also enhanced with other features fromthe above description and/or the already existing claims, is claimed fora pencil for applying a coloring and/or cosmetic substance, having apigment core composed of the substance that is to be applied and aone-piece injection-molded casing encompassing the pigment core that iscomposed of a thermoplastic material that consists of a mix of a firstplastic and a second plastic and that features the fact that after theouter circumference surface is cut into in such a way that a shavingprotrudes from the outer circumference, it is possible to peel a skinoff the surface of the casing by pulling on the shaving with the unaidedhand.

Independent protection, possibly also enhanced with other features fromthe above description and/or the already existing claims, is claimed fora pencil for applying a coloring and/or cosmetic substance, having apigment core composed of the substance that is to be applied and aone-piece injection-molded casing encompassing the pigment core that iscomposed of a thermoplastic material that consists of a mix of a firstplastic and a second plastic and the pencil features the fact that itscasing has a structure composed of two layers that can be separated fromeach other by hand and preferably, the one of these two layers that iscloser to the surface is thinner.

Independent protection, possibly also enhanced with other features fromthe above description, is claimed for a pencil for applying a coloringand/or cosmetic substance, having a pigment core composed of thesubstance that is to be applied and a one-piece injection-molded casingencompassing the pigment core that is composed of a thermoplasticmaterial that consists of a mix of a first plastic and a second plastic,and which pencil features the fact that its casing, viewed in the radialdirection, has an outer enrichment zone with a higher concentration ofthe first plastic than in the middle region.

In this regard, it should be noted that the formation of an innerenrichment zone, possibly through a suitable temperature control at theinner circumference of the casing can be achieved. In instances in whichthis claim is in force, the above statements apply analogously and onlycertain limitations, which are based in the inner enrichment zone (whichis not present or is purely optional in this variant), are omitted.

Independent protection, possibly also enhanced with other features fromthe above description and/or the already existing claims, is claimed fora pencil for applying a coloring and/or cosmetic substance, having apigment core composed of the substance that is to be applied and aone-piece injection-molded casing encompassing the pigment core that iscomposed of a thermoplastic material that consists of a mix of a firstplastic and a second plastic, and which pencil features the fact thatits casing, viewed in the radial direction, has an inner enrichment zonewith a higher concentration of the first plastic than in the middleregion.

In this regard, it should be noted that the formation of an outerenrichment zone, possibly through a suitable temperature control at theouter circumference of the casing can be achieved; the thermal energythat is no longer needed after the injection into the cavity is thenremoved from the plastic compound of casing essentially via its innercircumference surface. In instances in which this claim is in force, theabove statements apply analogously and only certain limitations, whichare based in the outer enrichment zone (which is not present or ispurely optional in this variant), are omitted.

REFERENCE NUMERAL LIST

-   1 pencil-   2 casing-   3 cross-section of the casing-   4 outer circumference-   5 inner circumference-   6 outer enrichment zone-   7 inner enrichment zone-   8 pigment core-   9 seat-   10 closing cap-   11 silicone stopper-   12 cone-   100 measurement point 1-   200 measurement point 2-   L longitudinal axis of the pencil and its casing-   S shaving-   D thickness of the skin-   A detachment length-   Pi cone angle

The invention claimed is:
 1. A pencil for applying a coloring and/orcosmetic substance, comprising: a pigment core composed of the substancethat is to be applied and a one-piece injection-molded casingencompassing the pigment core that is composed of a thermoplasticmaterial that consists of a mix of a first plastic and a second plasticthat are mixed with each other; wherein the casing, respectively viewedin a radial direction, has an outer enrichment zone with a higherconcentration of the first plastic than in a middle region of thecasing; and the casing, respectively viewed in the radial direction, hasan inner enrichment zone with a higher concentration of the firstplastic than in the middle region.
 2. The pencil of claim 1, wherein theconcentration of the first plastic decreases continuously from the outerenrichment zone and from the inner enrichment zone toward the middleregion.
 3. The pencil of claim 1, wherein over at least 80% of itscross-section area, the plastic casing is composed of both the first andthe second plastics, with the two plastics being encountered inpercentages by weight that differ by location.
 4. The pencil of claim 1,wherein the casing consists predominantly, at least 85% by weight, ofthe first and second plastics, plus any fillers and auxiliary materialssuch as pigments.
 5. The pencil of claim 1, wherein one of the first andsecond plastics is a weakly polar plastic with an electron negativitydifference ΔEN in the range 0.3≤ΔEN≤0.5.
 6. The pencil of claim 1,wherein one of the first and second plastics is a strongly polar plasticwith an electron negativity difference ΔEN in the range 0.5<ΔEN≤1.7. 7.The pencil of claim 1, wherein the first plastic is an AES.
 8. Thepencil of claim 1, wherein the second plastic is a TPE.
 9. The pencil ofclaim 1, wherein the thermoplastic material comprising the casing is setup so that the first plastic has a weight proportion of at least 45% byweight.
 10. The pencil of claim 1, wherein an upper limit for the firstplastic in the injection-ready mix is 85% by weight.
 11. The pencil ofclaim 1, wherein at an outer circumference surface, the casing has amathematically determined gloss level GU of more than 30 GU.
 12. Thepencil of claim 1, wherein the casing has a structure composed of twolayers that can be separated from each other.
 13. The pencil of claim 1,wherein the plastic casing consists of a non-foamed plastic.
 14. Thepencil of claim 1, wherein the casing is embodied in the form of a tubethat is open at both ends.
 15. The pencil of claim 1, wherein at oneend, the casing tapers conically.
 16. The pencil of claim 1, wherein atone end, the casing has a shoulder with a reduced diameter.
 17. Thepencil of claim 1, wherein at an end of the pencil, an end cap isfastened; which closes one end of the casing.
 18. A method for producinga pencil with a casing according to claim 1, comprising the steps of: aplasticized, injection-moldable compound is produced, composed of afirst and second plastic material that are completely mixed with eachother, the plastic materials are chosen so that they have solidificationbehaviors that differ from each other such that they separate when theycome into contact with a cooled mold surface, the compound is injectedat a high pressure of at least 900 bar into a mold cavity of aninjection mold forming the casing of the pencil, with the injection moldbeing intensively cooled such that directly against its wall surfacethat produces the mold cavity and over the entire length of the moldcavity, predominantly the first plastic material solidifies and is thusenriched against the wall surface, and then the two plastic materials ina region of the casing, which is underneath a region of an outercircumference surface of the casing, solidify together with lessseparation than in the region of the outer circumference surface orwithout any separation.
 19. The method of claim 18, wherein in theregion of the outer circumference surface of the casing, no mold partingline is formed by the injection mold.
 20. The method of claim 18,wherein the completely injection molded casing is ejected from the moldin the direction of its longitudinal axis L.
 21. The method of claim 18,wherein a pigment core receptacle in a center of the casing is formed bya pin that constitutes a mold core, which is removed together with thecasing when the casing is ejected from the injection mold.
 22. Themethod of claim 18, wherein the wall surface of the injection mold thatforms the outer circumference surface of the casing has a roughnessdepth Rz≤5 μm.
 23. The method of claim 18, further comprising casting apigment core, wherein the casing is inserted into a mold that seals thecasing at a tapering end of the casing and that forms a subsequent shapeof an unused tip of the pigment core, and a compound that forms thepigment core is poured in at the other end of the casing.